1. Field of the Invention
The present invention relates to a sub headlight unit and a sub headlight system for use in a vehicle that leans into turns, and to a vehicle that leans into turns.
2. Description of the Related Art
In general, in a vehicle that leans into turns (such as saddle-ride type vehicles including motorcycles, three-wheeled motor vehicles, snowmobiles, and ATVs (all terrain vehicles), for example), when the vehicle corners or turns at an intersection, a rider operates a handlebar and additionally shifts his/her own weight in order to counteract centrifugal force acting on a vehicle body. As a result, the vehicle turns with an attitude (hereinafter, also referred to as “lean attitude”) leaning to the inner side of a curve. On the other hand, in a vehicle that does not lean into turns, for example, in an automobile, when the vehicle corners or turns at an intersection, a rider operates a steering wheel and the vehicle turns with centrifugal force acting on a vehicle body thereof. Therefore, in the vehicle that does not lean into turns, the vehicle body leans to the outer side of a curve due to the centrifugal force.
In the vehicle that leans into turns, the turning is made with an active use of the weight shifting of the rider himself/herself. Therefore, the vehicle body largely leans. In the vehicle that does not lean into turns, the vehicle body leans to the outer side of the curve due to the centrifugal force. The degree of this leaning varies depending on the running speed of the vehicle and the magnitude (radius) of the curve, and this leaning of the vehicle body is not utilized for the turning. In the vehicle that does not lean into turns, it is preferable that the amount of leaning to the outer side of the curve due to the centrifugal force is small.
Thus, at a time of cornering or turning at an intersection, the vehicle that leans into turns causes the vehicle body to lean to the inner side of the curve with a relatively large amount of leaning, while the vehicle that does not lean into turns causes the vehicle body to lean to the outer side of the curve with a relatively small amount of leaning.
Normally, a vehicle is provided with a plurality of lights irrespective of whether or not the vehicle leans into turns. The lights include a light intended mainly to ensure a field of view of a rider of the vehicle and a light intended mainly to enable a surrounding vehicle or the like to recognize the presence of the rider's vehicle. A headlight is the light intended mainly to ensure the field of view of the rider of the vehicle, and in general, is configured to switch between a high beam (running headlight) and a low beam (passing headlight).
The high beam, which emits light in a horizontal (upward) direction, ensures a field of view at a long distance. Generally, in order to avoid blinding or impairing the vision of a rider of a nearby or oncoming vehicle, the high beam is used in a situation where there is no vehicle or the like existing ahead at night. The low beam, which emits light in a downward direction, is used even in a situation where there is a vehicle or the like existing ahead. Therefore, in a normal case, a vehicle often runs with the low beam turned on.
When the vehicle that leans into turns is running on a straight road, an illumination range of a headlight light source (low beam) spreads evenly to the left and right in an area ahead in an advancing direction and below a horizontal line of the headlight light source. When the vehicle that leans into turns is running on a road curving to the left, the vehicle runs with the vehicle body inclined to the left. Accordingly, the illumination range of the headlight light source spreads downward to the left. As a result, a nearer position on a running lane is illuminated. Thus, the illumination range in an area inside the curve and ahead in the advancing direction is reduced.
Therefore, a vehicle has been proposed in which, in addition to a main headlight that illuminates an area ahead of the vehicle, a pair of right and left sub headlights that are turned on depending on the magnitude of a lean angle (angle of inclination of a vehicle body to the inner side of a curve relative to an upright state thereof) are provided as the headlight (Japanese Patent No. 4806550). When the vehicle body is in the upright state, illumination ranges of the pair of right and left sub headlights are located above a cut-off line (which is a boundary line that defines the upper edge of the illumination range) of the main headlight, but the sub headlights are not turned on when the vehicle body is in the upright state. That is, in the vehicle disclosed in Japanese Patent No. 4806550, when the lean angle of the vehicle body increases and reaches a predetermined value, the sub headlights, which are arranged at the inner side of a curve, are turned on, while when the lean angle of the vehicle body decreases and falls below the predetermined value, the sub headlights are turned off.
In this manner, when the lean angle is large, the sub headlights shown in Japanese Patent No. 4806550 ensure a wide illumination range in an area inside a curve and ahead in the advancing direction, thus improving the visibility ahead in a path at a time of running along a curve. On the other hand, as described above, the sub headlights are directed upward, and have a relatively high brightness for improving the visibility ahead in a path. Therefore, when the lean angle is small, the sub headlights are turned off, to prevent blinding or impairing the vision of, for example, a rider of a nearby or oncoming vehicle.
Thus, the sub headlight shown in Japanese Patent No. 4806550 is a device useful for the vehicle that leans into turns, because the sub headlight has a function for adjusting a brightness level in accordance with the lean angle, to thereby ensure a wide illumination range in an inside area ahead in an advancing direction with suppression of glare.
Meanwhile, in the field of vehicles, from the viewpoint of the running performance and energy efficiency, it is generally desired that a vehicle body is a lightweight and its size is not more than required. Particularly, in the vehicle that leans into turns, downsizing of a vehicle body is quite strongly demanded for the reason that, for example, the attitude of a vehicle body is controlled by the weight shifting of a rider. Therefore, even the useful device as shown in Japanese Patent No. 4806550 is not easily allowed to be mounted on the vehicle body. Instead, it is desired that one device serves a plurality of functions.